Electrical resistance device



Aug. 21 1934. L.'W. THOMPSON 1,

ELECTRICAL RESISTANCE DEVICE Filed Feb. 25. 1932 Fig. I 20 Louis W.Thohwpsoh,

M. His Att rnegf Patented A... 21, 1934 UNITED STATES 1.971.204ELECTRICAL nasrs'mucs DEVICE Louis W. Thompson, Schenectady, N. Y.,assignor to General Electric Company, a corporation of New YorkApplication February '25, 1932,'Serlal No. 595,070 9. Claims. (01. 201-55) My invention relates to electrical resistancedevices, and moreparticularly to improvements in electrical resistance devices of thetype em-- able resistance device in which a main control device isarranged to respond to variations in a condition to'be regulated, it isusually desirable to have a variable resistance device which ischaracterized by ruggedness, long life, freedom from 5 contact arcingand deterioration, ease of movement from one extreme position to theother, and small amount of movement between extreme po sitionscorresponding respectively to the maximum and minimum resistance.

In accordancewith my invention, I provide an improved resistance devicewhich is characterlzed by the above featurs and which, in addition,includes additional improved features which will 'bedescribed more fullyhereinafter.

new and improved electrical resistance device.

It is another object of my invention to provide an electrical resistancedevice which is characterized by long life, minimum mechanicalresistance to change of electrical resistance, and .a minimum requiredmechanical movement for a maximum change in electrical resistance.

My invention will be better understood from the following descriptiontaken in connection with the accompanying drawing, and its scope will bepointed out in the appended claims.

In the drawing, Fig. Us a front elevation, partly in section, of anautomatic voltage-regulator employing my invention; Fig. 2 is an endelevation of the regulator shown in Fig. l, as viewed from the left-handend of Fig. 1; Fig. 3 is an enlarged detail section of my resistanceregulator taken on line 3-3 of Fig. 1; Fig. 4 is a longitudinalsectional view of my resistance regulator taken when the resistanceelement thereof is in a verti cal position, and Fig. 5 is a sectionalview .of

K Fig. 4 taken on the line 5-5 of Fig. 4.

' Referring now to the drawirfg,. wherein the same reference charactersdenote the same elements throughout the various figures, and referringparticularly to Figs. 1 and 2, I show a panel board 1, of any suitablematerial, on'which to mount the regulator. Mounted on panel 1 is a Icontainer, or envelope 2, which is preferably made of anelectrical'i'nsulating materiaLsuit- It is an object of my invention toprovide a;

this combination is so mounted in container 2 able materials being suchvitreous compositions as glass, pyrex,-.porcelain, etc. Container 2 ispivotally mounted on panel board 1 in any suitable manner andas shown,it is mounted in a frame 3, by means of straps 4, the frame 3 carryingknife-edge projections 5, which cooperate with suitably notched brackets6, fastened to panel board 1. Container 2 may take a variety of shapesso long as the lowermost parts of its cross section, taken perpendicularto its axis of rotation, are internally substantially circular in'shape. The simplest and perhaps the best shape of such a container is anelongated cylinder, is illustrated.

Mounted in container 2 are a quantity of an electrically conductingfluid 7 and a solid electrical conductor 8. These conductors are soarranged that when the container 2 is in one position the solidconductor will be in engagement with the fluid conductor throughoutsubstantially the entire'length of the solid conductor, while when thecontainer is rotated to another position, the solid conductor willengage the fluid conductor 'at substantially only a few points on thesolid conductor. The fluid and solid conductors may both be composed ofelectrical resistance material or either one alone may be composed ofrelatively high resistance material while the other is of relatively lowresistance material. I have found, however, that best results areobtained when the fluid. conductor is of relatively low electricalresistance as compared with the electrical resistance of the solidconductor. Thus, in a preferred arrangement of my invention, the fluidconductor 7 is liquid mercury, while the solid conductor 8 may be anywell known relatively. highv resistance material. Resistance conductor 8may be of almost any desired type or shape, but I'havefound that goodresults are obtained when it is in the form of a resistance wire whichis wound ona suitablev supporting means which I have illustrated as anin- Oil . sulating strip 9. Resistance wire. 8 and strip 9 may togetherbe taken as a solid resistance and 1 0 that itscontact boundary is inparallel relation with the longitudinal axis of the container. As shown,the resistance element is so mounted that its longitudinal axis makes arelatively small angle with the .axis of rotation of the container.

A convenient way of mounting the combination of resistance wire 8 andsupporting strip 9, is by meansof metallic plate members 10 which are ofa. circular shape and of such a size as to fit snugly within thecontainer 2. As shown clearly in Fig. 4, the longitudinal axis of thesolid resistance element, comprising the wire 8 wound on the support 9,makes a small angle with the axis of rotation of the container. It is bymeans of this angle that rotation of the container will cause varyingdegrees of submergence, or progressively changing points of contact, 0the solid resistance material in or with the liquid conducting material.As shown in Figs. 1, 2 and 3, the container 2 is in such a position thatthe resistance wire 84s just making contact with the mercury 'l at theleft-hand end of the resistance. It now the container 2 is rotated in aclockwise direction as viewed in Figs. 2 and 3, the direction of motionof the contact boundary of resistance 8 will be substantially at rightangles to its longitudinal axis and the point of contact betweenresistance 8 and the surface of the mercury will move toward the rightthereby causing successive engagement of the turns of the resistancewire with the mercury.

The left-hand end of resistancewire 8 is electrically connected at 11 tothe metal supporting plate 10 so that this end of the resistance wire isin electrical contact with the mercury '7 The right-hand end oftheresistance wire 8 is connected to a terminal 12 which is insulatedfrom the right-hand supporting member 10. Another terminal 13 iselectrically connected to the supporting means 10. Lead-in wires 14connect respectively to the terminals 12 and 13 and these lead-in wires14 are sealed into the walls of the container in a manner similar tothat in which the lead-in wires to an ordinary incandescent electriclight bulb are sealed in.

with these connections'and with the resistance regulator in the positionshown'in Figs. 1, 2 and 3,

an electrical circuit through the regulator will begin, for example, atterminal 12, traverse substantially all of the resistance wire 8 andreturn through the mercury to the terminal 13. As the container 2 isrotated in a clockwise direction, as viewed in Figs. 2 and 3, the pointof contact of the resistance .and the mercury is moved to the right,thereby short circuiting successive turns of the resistance 8 andreducing simultaneously the length of the conducting path through boththe resistance wire 8 and the conducting liquid 7.

In assembling the regulator, the container 2 will be open at itsright-hand end and the strip 9 with its attached supports 10 will heslid into the container, electrical connections will then be completedbetween the lead-in wires 14 and the terminals 12 and 13 respectively,and then the container will be sealed at points 15.

In order to .prevent oxidation and deterioration of the resistance wire8 and also to prevent arcing between the resistance wire and themercury, the container 2 may be evacuated or it may be -fllled with anatmosphere of oxidation preventing gas. This gas may actually beareducing gas such as hydrogen or it may be a relatively inert gas suchas argon, helium or nitrogen.

I have found that with the above described arrangement relatively suddenchanges in the angular position of the container 2, which result invarying the degree of engagement of the resistance wire on strip 9 withthe liquid in the container, cause traveling ripples to move alon thesurface of the liquid. These traveling ripples cause undesirable anduncontrollable resistance changes. By providing one or more spacedbailles 16 which extend into the liquid conductor, these ripples areeifectivelybroken up and a distinct improvement in operation results.These bafiies may be supported in any suitable way and as shown Iprovide wires, or rods, 17 for this purpose. These wires are fastened tothe end supporting plates 10.

With the resistance device described above, it will be seen that in noposition can the resistance of the regulator exceed the combinedresistances of the resistance wire 8 and the return circuit through theliquid. This is because even if the resistance wire 8 is entirely out ofcontact with the mercury, the return circuit will always be made throughthe left-hand end plate 10 to the mercury. This is a distinct advantageas it prevents accidentally open circuiting a regulating circuitincluding the regulating resistance.

It will also be noted that as the container 2 is rotated from itsposition corresponding to maximum resistance to its positioncorresponding to minimum resistance of the regulator, the length of theelectrical conducting paths through the solid and the liquid conductorsvary simutaneously and similarly, that is to say, their maximum andminimum lengths occur together. While this is not of much advantage incases where the fluid conductor is mercury, because of the relativelylow resistance of this liquid, it is of considerable advantage in caseswhere the electrical resistance of the solid and fluid conductors aresubstantially equal.

Another advantageous result which I obtain is that the fluid, or liquid,conductor does "not have to be moved in changing the resistance of theregulator and consequently the inertia forces produced when theregulator goes from one position to the other may be made relatively lowbecause in cases when the liquid conductor is mercury, the remainingelements will be relatively light in comparison with the mercury.

It will also be seen that my resistance regulator will be balanced inany position so that it will require but a relatively small and uniformforce to change it from any one position to another.

As shown in Fig. 1, I have illustrated an application of my invention toan automatic electric voltage regulator. In this figure a solenoidmagnet 18 is connected across a circuit 19 whose voltage is to beregulated. The core 18:; of solenoid magnet 18 is mechanically connectedto the frame 3 for operating my resistance device. A suitable rheostat20 is connected in the energizing circuit of solenoid 18 for adjustingthe voltage calibration of this solenoid. For energizing circult-19 Ihave illustrated a direct current generator 21 having a shunt fieldwinding 22 whose circuit is connected to the terminals 14 of myresistance device. A conventional shunt field rheostat 23 isalsoprovided in the shunt field winding circuit of the generator. Arestraining spring 24, for opposing the pull of solenoid 18, is-

connected to the frame 3. The solenoid 18 is made extra large andpowerful so thatit will develop operating forces on changes of voltageof circuit 19 which are sufficiently large to readily and quickly rotatemy resistance device. The core 180 of the solenoid is so arranged thatas it is pulled up into the magnet from its lowermost position it entersa stronger and stronger magnetic field, so that with a constant voltageapplied to the terminals of the operating magnet the pull on thesolenoid core increases as the core moves up into the magnet. If flatregulation is desired spring 24 is so constructed that its change inpull, as a is stretched due to the rotation of the resistance device,exactly equals the change in pull of the solenoid magnet resulting fromits change of poconnected in parallel.

As shown in Fig. 1, the core 18a is in its uppermost position and theresistance device is in its maximum resistance position. Assume,however,

'thatthese devices are in substantially their middle positions and thatthe voltage on circuit 19 is normal. If now circuit conditions shouldshould'increase, the voltage of circuit 19 would decrease therebydecreasing the pull of the solenoid 18, and allowing the spring toovercome the pull of the solenoid, thereby rotating the resistancedevice and decreasing its resistance. This increases the current throughthe field winding 22, thereby increasing the voltage of genorator 1 andincreasing the voltage of circuit 19. As soon as the voltage of circuit19 returns to normal, the regulator will come to rest in its balancedposition because in this new position the pull of the spring and thepull of the solenoid will balance each other. Similarly, if the voltageof circuit 19- increases, the pull of solenoid 18 increases, therebyrotating the resistance device in the opposite direction and increasingthe value of the resistance of the resistance device, thereby.

' decreasing the voltage of the generator 21. When the voltage returnsto normal the regulator will balance in its new position.

In order to-prevent hunting of the regulator-I provide a suitabledashpot mechanism 25, which is connected through a spring 26 to frame 3.Introduction of spring 26 is to permit rapid, relatively small changesin resistance of the regulator, thus increasing the speed of operationof the regulator.

While I have shown and described a particular embodiment ofmy'invention, it will be obvious to those skilled in'the art thatchanges and modifications may be made without departing from myinvention, and I therefore aim in the appended claims to cover all suchchanges and modifications as fall within the true spirit and scope of myinvention. I

What I claim as new and desire to secure by Letters Patent in the UnitedStates is:

1. A variable resistance device comprising a horizontaltubular containerhaving a longitudinal axis of rotation, an electrical conducting fluidpartially filling said container to a substantially constant levelandarranged for relative movement with said container, and an electricalresist-- change, for example, if the load on circuit 19v tive movementtherewith, and an electrical resistance within saidcontainer in fixedrelation therewith and having a longitudinal contact boundarysubstantially co-extensive with one of the dimensions of the surface ofsaid liquid and arranged so that points of contact with said liquidchange progressively along said boundary in accordance with the relativemovement between said fluid and container.

3. In combination, a substantially horizontal cylindrical container, arelatively low resistance electrical conducting liquid partially fillingsaid container, means for rotating said container about its longitudinalaxis, a relatively high resistance electrical conducting element mountedin said container in such a manner that said rotationcauses varyingdegrees of submergence of said element in said liquid, said elementhaving a contact boundary making a small angle with the surface of saidliquid.

4. In combination, a liquid electrical conductor, a solid electricalconductor mounted for variable engagement with said liquid conductor,and a bailie normally associated with the surface of said liquidconductor for breaking up traveling ripples on the surface of saidliquid conductor.

5. In combination, a liquid electrical'conductor, a solid electricalresistance element arranged variably to engage the surface of saidliquid along the length of said conductor at an effective angle withrespect to the surface of said liquid which is small, and spaced bafflesassociated with the surface of said liquid for breaking up travelingripples on the surface of said liquid.

6. In combination, an elongated glass tube, supporting means formaintaining the longitudinal axis of said tube substantially horizontaland for permitting rotation of said tube about said axis, a strip ofinsulating material mounted in said tube in such a manner that itslongitudinal axis makes a relatively small angle with the axis of saidtube, an electrical resistance wire wound on said strip, a suflicientquantity of liquidmercury in said tube to cause engagement between saidmercury and substantially all of the turns of said resistance wire whensaid strip is vertical, bailles placed at intervalsin said tube to breakup longitudinally traveling ripples on the surface of said mercury, andan atmosphere of reducing gas in said tube.

'7. In combination, a straight elongated glass tube having itslongitudinal axis substantially horizontal, supporting means forpermitting rotation of said tube about its longitudinal axis, a straightrelatively thin elongated rectangular strip of insulating materialrigidly mounted in said tube with its longitudinal axis making arelatively small angle with the longitudinal axis of said tube, aresistance wire wound around said strip substantially perpendicularly toits longitudinal axis, a suflicient quantity of liquid mercury in saidtube to just permit engagement between said mercury and a portion ofsubstantially ance within said container in fixed relation therewith andhaving a longitudinal contact boundary for engagement with said fluid,said contact boundary making an acute angle with the longitudinal axisof said container.

2. A variable resistance device comprising a container, an electricalconducting liquid partially filling said container and arranged forrelaeach of the turns of said resistance wire when said strip is in asubstantially vertical position, baffle plates mounted at intervals insaid tube in engagement with the surface 'of said mercury;

cylinder whose axis corresponds with the axis of said container, aresistance element having the substantial equivalent of a straight linecontact said container, said strip having one edge which is a straightline making a small angle with said axis, a resistance wire wound aroundsaid strip, and a. quantity of conducting liquid in said container forengagement with said resistance wire.

LOUIS w. momson.

